The invention relates to a method of placing and consolidating a mass of particulate material in a permeable subsurface formation or reservoir and/or a well penetrating the formation. The invention also relates to a composition for carrying out said method.
The present invention relates to treating a formation (and/or a well penetrating such a formation) having fluid in the pore space thereof. Such fluid may be a hydrocarbon liquid, hydrocarbon gas or other gas, water or other liquid and may have chemical compounds dissolved therein. The reservoir fluid may be valuable and may be recovered, or the method may be carried out in a subsurface formation that is to be used for storing fluids, such as waste liquids.
The presence of a consolidated mass of particulate material in or around a well penetrating a subsurface reservoir formation may be desirable for various reasons, such as for preventing closure of fractures that have been made in the formation, for preventing the influx of formation grains into the well, and for filling up cavities around the well, which cavities have been formed during a preceding fluid recovery period wherein formation grains have been entrained by fluid passing from the formation pore space into the well.
Most frequently, a consolidated mass of particulate material is used to prevent the entrainment of formation particles in fluid flowing from the formation into the well. Particles entrained in such fluid will easily locally erode conduits such as the casing or the production tubing in a well, the flow lines on the surface, and/or choke the flow passage in the well or in the conduits communicating with the well. Costly repairs or well cleaning treatments are then required to bring the well into production.
Various methods are known for placing a particulate material in a well and/or a subsurface formation. Such particles are often transported through the well by means of a carrier fluid, and after a mass of the particles has been in the well or the formation, a consolidation treatment is effected to form a bond between the particles. Resins or resin-forming materials are preferred as a bonding agent, and may be injected in liquid form (for example, by dissolving them in a liquid) into the pore spaces of the mass of particulate material after it has been placed. However, a uniform distribution of the resin over the particles forming the mass to be consolidated is often difficult to achieve by such a procedure. A more uniform coating is obtained by pre-coating the particles with a resinous material and, after emplacing the coated particles, allowing or causing the hardening of the resinous material.
In the prior methods, the resinous bonding agent materials have consisted of viscous liquid layers around the particles and have often contained both a resin-forming material and a curing agent for causing the hardening or curing of the resin. For example, the following U.S. patents have described the following procedures:
U.S. Pat. No. 2,815,815 describes injecting an oil slurry of sand coated with a mixture of resin-forming liquid and curing agent.
U.S. Pat. Nos. 2,941,594 and 3,123,137 describe injecting particles coated with a liquid-stage hardenable or solidifiable epoxy, phenolic, or the like, resin which will become hard on standing or when contacted by a hardener.
U.S. Pat. No. 2,981,334 describes injecting sand coated with a stage B phenolic, epoxy, or the like, resin mixed with metal particles which are subsequently acidized to heat the positive mass of particles.
U.S. Pat. No. 2,986,538 is similar to the 2,981,334 patent, using epoxy resins which are first partially hardened and then quenched.
U.S. Pat. No. 3,335,796 describes injecting particles which are first pre-coated with a cured resin and then re-coated with a liquid resin which is cured after the particles are deposited.
U.S. Pat. Nos. 3,621,915; 3,867,986 and 3,878,893 describe injecting suspensions of particles, epoxy resin-forming materials, and curing agents, in an oil solvent which is only partially miscible with the solvents for the resin-forming components.
U.S. Pat. No. 3,929,191 describes injecting sand coated with alkali-catalyzed phenolic resins which are solid at surface temperatures but soften and then cure at the reservoir temperature.
U.S. Pat. No. 4,127,173 describes injecting sand coated with hardenable resin material around a shaped pipe, hardening the resin, and then removing the shaped pipe.
However, since the epoxy resin-forming materials heretofore used for precoating such particles include a hardener, the storage time of the coated particles is rather restricted, even at relatively low surface temperatures. Moreover, if a mass of such precoated particles becomes stuck or misplaced in the well (such as may happen when failure of the pumps occurs), the resin will soften and the velocity of the reaction between the resin and the hardener will increase. While the reaction velocity may be rather low at surface conditions, when the particles are subjected to the temperature at the depth at which the reaction velocity may be high, a mass of the particles may be consolidated at an undesired location from which the mass either cannot be removed, or can be removed only at great cost.
Further, a prolonged storage period of particles coated with a mixture of epoxy resin and a latent, modified curing agent, such as a polyamide hardener, is often harmful to the quality of the consolidated mass to be formed by this material, in particular when the prolonged storage takes place in areas with tropical or sub-tropical climate.
The object of the present invention is to provide a method of placing and consolidating a mass of particles in a well and/or an adjacent reservoir formation by using particles coated with a further polymerizable solid epoxide having a softening point and reactivity arranged so that the coated particles can be transported and stored over long periods at the surface temperature without causing a deterioration of the coating or the strength of the consolidation which is subsequently provided.
Another object of the invention is to provide an economic, efficient and safe method of placing and consolidating a mass of particulate material in or around a well or borehole in a subsurface formation.